1.0 Field of the Disclosure
This disclosure relates generally to cartridges for ammunition. In particular, exemplary embodiments are directed to multiple projectile cartridges having an insert arranged within the cartridge casing which includes an interior cavity for supporting one or more projectiles.
2.0 Related Art
Multiple projectile fixed cartridge loads are conventionally referred to as duplex (e.g., two projectiles) or triplex (e.g., three projectiles) loads. Such duplex and triplex loads, when used in a bottleneck casing (e.g., a centerfire rifle casing), can have a plurality of shortcomings. For example, some conventional multi-projectile cartridges have lacked support for one or more projectiles within the casing, which can create problems in maintaining proper projectile alignment, such that accuracy and precision of each of the projectiles may be reduced.
Internalized support structures have been developed for multiple projectile loads generally through the use of recesses formed along a central axis of each projectile. In addition to providing a nested fit between successive rounds, the recesses further may be configured to support a rod, pin, or other alignment device which engages the plurality of projectiles and maintains proper alignment therebetween. However, the use of such tight mating recesses and additional support structures can significantly increase the complexity and cost of manufacture of the projectiles. For example, imperfection in the concentricity or shape of the recesses results in a static and dynamic mass imbalance of individual projectiles. Mass imbalance localized near the rear of a projectile can be particularly harmful to accuracy of the rounds by causing compounding effects on projectile dispersion. Furthermore, due to inherent variations in manufacturing tolerances it is very difficult to form heel cavities or recesses that do not result in some level of mass imbalance.
Assembly of conventional multi-projectile cartridges also can be complicated due to the accuracy necessary in alignment of the multiple projectiles. Oftentimes the projectiles are inserted within a casing as a single unit in a single step, thus requiring substantially precise alignment prior to insertion within the casing. Thereafter, upon firing, presentation of expanding combustion gases to the different projectiles can lead to issues in the accuracy of such projectiles. For example, conventional duplex and triplex loads can lack control in presenting expanding combustion gases to a volume of space between two or more projectiles, thus creating further inaccuracy due to differences in gas pressures acting upon each projectile of the multiple projectiles.
Further complications can arise in the use of multiple projectiles for subsonic loads (e.g., loads presenting a muzzle velocity below the speed of sound). Most conventional weapon systems typically are optimized for the use of supersonic ammunition (e.g., loads presenting a muzzle velocity above the speed of sound). When use of subsonic ammunition is attempted in such weapon systems, malfunctions can occur due to the energy generated by the reduced velocity load being insufficient to reliably cycle the weapon. Typical design changes to counter this deficiency are increasing projectile velocity, increasing propellant mass, and/or increasing projectile mass. Each option has traditionally had substantial shortcomings. Increasing projectile velocity in subsonic loads is by definition constrained. Increasing propellant mass for the same projectile velocity is wasteful/costly. Increasing the mass of a single projectile for any given caliber requires either lengthening the projectile, which typically hinders accuracy due to instability, or constructing the projectile of higher density materials, which usually results in an increased cost.
Accordingly, a need exists for increased accuracy, decreased production costs, and improved weapons functionality in multiple projectile fixed cartridge designs.